too many defects to solve in a year

How about implementing a 'test first' strategy? 

https://www.scrum.org/resources/blog/if-you-are-not-doing-test-first-th…

I guess I'm not really sure what the problem is. It seems like you have your defect work ordered in your Product Backlog so you can achieve the right balance between defect fixing and new development to meet the needs of your stakeholders. If you want to fix more defects in less time, then you would have to do less new development and spend more time fixing defects.

The other aspect is to take steps to prevent defects from happening in the first place. There are techniques to improve the design of the product and increase its testability. There are also changes that can help to make quality everyone's responsibility and build quality in at every step in the process. When defects do happen, using root cause analysis on specific defects can supplement retrospectives to find opportunities to improve both the product and processes.

Every team has at least 120 different defects... From which point me and system architect, chief PO, POs, developers can start to facilitate discussion and take actions together with development team?

From the point where a Nexus of Scrum Teams is recognized, in which each team has a shared view of what Done ought to mean for the Product. The defects you describe ought to be accounted for on the Product Backlog so the teams can adopt a policy for their remediation.

The people you mention may have responsibilities to fulfil on the Nexus Integration Team with regards to integration assurance, and providing transparency over Done so each future increment is defect-free. 

I am working as a Scrum Master and I want to decrease the amount of defects for our product.

While I admire your desire, this sounds more like a activity that the Developers and Product Owners own.  Scrum Masters focus on the ability of the Scrum roles to function effectively and the organization to understand how to support them.  This activity is about maximizing the value of the work being done by the Developers. It is also about the Developers taking responsibility for the quality of their work and addressing the technical debt that they have accumulated.

As a Scrum Master you can help in this effort by helping the Product Owner understand how to manage the Product Backlog to maximize the value of the work done by the Developers.  You can help the Developers understand how to effectively represent the technical debt to the Product Owner so that individual can understand the value of addressing it.